[AMRadio] Trouble brewing ...


Brett Gazdzinski b.gaz at comcast.net
Tue Dec 17 17:48:16 EST 2013


Any of the sdr receivers do that.
Sync, both or one sideband, AM, or dsb.

Some programs are better then others, you just click the button and get one 
sideband, the other, or both.
Powersdr has some of the worst properties, sdr-radio works real well, hdsdr 
is in the middle.
hdsdr has added an AFC button that works in regular AM or sync AM, it tunes 
in the carrier zero beat by itself.

The filters are so sharp, its very useful to listen to only one sideband 
many times.
With powersdr, you have to drag the filter over manually, and it has no afc 
feature.

Brett
N2DTS

----- Original Message ----- 
From: "Bry Carling" <bcarling at cfl.rr.com>
To: "Donald Chester" <k4kyv at charter.net>
Cc: <amradio at mailman.qth.net>
Sent: Tuesday, December 17, 2013 8:30 AM
Subject: Re: [AMRadio] Trouble brewing ...


> Don
>
> From a practical standpoint, can you tell us which commercial ham 
> receivers or HF capable receivers have a synchronous detector like that?
>
>
>
> Bry Carling
> http://af4k.com
> Sent with my iPhone 6
>
>
>> On Dec 17, 2013, at 3:40 AM, "Donald Chester" <k4kyv at charter.net> wrote:
>>
>>
>>>>>>> I once had asynchronous detector in a simple Sony ICF 2010 receiver. 
>>>>>>> It
>> was remarkably good on AM.
>>
>> Bry Carling
>> http://af4k.com
>> Sent with my iPhone 6
>>
>>
>>> On Dec 16, 2013, at 4:55 PM, "Brett Gazdzinski" <b.gaz at comcast.net> 
>>> wrote:
>>>
>>> That is why I love a sync detector that allows only one sideband
>> reception.
>>> It sounds just as good as normal with a lot less noise.
>>>
>>> Brett
>>> N2DTS >>>>>>
>>
>> Actually, a  synchronous detector is basically designed to receive both
>> sidebands, but with the full advantage of a product detector as opposed 
>> to
>> an envelope  detector. If the receiver has variable selectivity, it may 
>> be
>> narrowed to the point that only one sideband is received, which may be
>> useful for dodging interference.
>>
>> Some synchronous detector circuits have the internal capability of 
>> allowing
>> the reception of only one sideband, using the phasing method of sideband
>> rejection. But in this case it becomes nothing more than an old fashioned
>> "sideband slicer", not a true synchronous detector. The synchronous 
>> detector
>> functions by coherently demodulating both sidebands and vectorally adding
>> them at the detector output, so that they reinforce each other.
>>
>> The only advantage of a synchronous detector when used to receive only 
>> one
>> sideband of an AM signal, is that the PLL automatically locks the BFO 
>> onto
>> the carrier frequency, thus eliminating the frequency error of a manually
>> tuned BFO. Otherwise, this is nothing more than ordinary selectable 
>> sideband
>> reception; you could do the same thing using any receiver with a narrow 
>> i.f.
>> filter, BFO and product detector; just carefully zero-beat the carrier by
>> turning the main  tuning control, with the BFO set to the edge of the
>> pass-band. This cuts random noise in half, but reduces the signal by 6 
>> dB.
>> If the interference consists  only of random noise, the net effect is a 3 
>> dB
>> degradation of signal-to-noise ratio.
>>
>> Don k4kyv
>>
>>
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